1. Field of the Invention
The present invention relates to an electric current sensor, and specifically relates to an electric current sensor that measures a large electric current.
2. Description of the Related Art
As prior documents that disclose the configuration of an electric current sensor or a magnetic sensor, there are Japanese Unexamined Patent Application Publication No. 2007-108069, Japanese Unexamined Patent Application Publication No. 2005-517937 and Japanese Unexamined Patent Application Publication No. 2013-88370.
An electric current sensor described in Japanese Unexamined Patent Application Publication No. 2007-108069 includes a conductor including a pair of parallel units that have substantially equal and constant cross sections and extend in parallel a first distance away from each other, a coupling unit for coupling one ends of the parallel units, and a pair of terminal units. The terminal units are connected to the other ends of the parallel units, and extend away in an opposed manner a second distance, which is larger than the first distance. The terminal unit has a larger cross section than the parallel unit.
A magnetic sensor described in Japanese Unexamined Patent Application Publication No. 2005-517937 includes at least two magnetoresistive elements that are biased in a first direction by an integral type conductor, and are sensitive to a magnetic field component in a direction orthogonal to the first direction. The sensitivity of the magnetic sensor to a magnetic field is adjustable, and is related to the level of a bias current. In an electric current sensor, two of the magnetic sensors are attached to both sides orthogonal to a conductor through which an electric current to be measured flows.
An electric current sensor described in Japanese Unexamined Patent Application Publication No. 2013-88370 includes a magnetic sensitive element that outputs an output signal by an induction field from an electric current to be measured. The magnetic sensitive element has a sensitivity axis and a sensitivity effect axis orthogonal to the sensitivity axis. The sensitivity axis is disposed to have a certain angle with respect to the direction of the induction field. The sensitivity effect axis is disposed orthogonal to a flow direction of the electric current to be measured and the direction of the induction field.
The conventional electric current sensors are used in linear ranges in which a magnetic flux density, which is detected by a magnetic sensor having a Hall element, a magnetoresistive element or the like, and an output voltage are proportional. In other words, when measuring a large electric current that generates a magnetic field exceeding the linear range of the magnetic sensor, the conventional electric current sensor has a large measurement error, thus causing a reduction in measurement accuracy.
On the other hand, when an electric current sensor provided with a magnetic sensor having a wide linear range is used to measure a large electric current, measurement accuracy of a small electric current is lowered due to the low sensitivity of the magnetic sensor.